Abstract LB-212: Antioxidant therapy reprograms macrophages from protumor M2 to antitumor M1

Abstract

Abstract Macrophages (Mϕ) have high plasticity and can polarize to two extremes, pro-inflammatory M1 Mϕ and immuno-suppressive M2 Mϕ. In triple negative breast cancer, tumor-associated Mϕ (TAM) have a pro-tumor M2-like phenotype and are associated with decreased survival. Thus, it is vital to develop treatments to reprogram TAM away from protumor M2 Mϕ toward antitumor M1 Mϕ. A recent study reported a lipid peroxide scavenger selectively inhibits M2 Mϕ markers and cytokines. However, little is known about the differences in ROS metabolism between M1 Mϕ and M2 Mϕ. Our hypothesis is pro-tumorigenic M2 Mϕ possess a distinct profile of pro- and anti-oxidant enzymes, as well as a different sensitivity to ROS modulation versus the anti-tumor M1 Mϕ. Our results show M2 Mϕ, derived from primary human monocytes, have a significant 20-30% reduction in intracellular ROS levels versus M1 Mϕ by DCFH and DHE staining. Extracellular ROS synthesis was dramatically reduced by ~70% in M2 Mϕ, in part due to reduced mRNA expression of Nox2, Nox5, and their accessory protein CYBA in M2 Mϕ. Another contributing factor to lower ROS levels is that M2 Mϕ have significantly increased Catalase and Gpx4 mRNA expression, as well as increased Cu/ZnSOD and Gpx1 protein and activity. These data suggest M2 Mϕ have increased ROS metabolism versus M1 Mϕ, which may provide an advantage in the oxidative tumor microenvironment. Furthermore, EcSOD re-expression in MB231, a triple negative breast cancer cell line, inhibited the MB231-mediated increase in M2 Mϕ markers and decrease in M1 Mϕ markers. We moved forward utilizing Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE), a small molecule SOD mimetic, shown to have anti-tumor effects. MnTE treatment increased M1 Mϕ markers, IL-12b and CD86, while concurrently decreasing M2 Mϕ markers, IL-10, CD163, and CD206. MnTE also inhibited the ability of M2 Mϕ to inhibit T cell activation suggesting ROS is required for M2 Mϕ polarization and function. Increasing ROS levels by addition of exogenous H2O2, lead to increased M2 markers and decreased M1 markers, which implicates the oxidative tumor microenvironment in promoting a M2-like TAM phenotype. These studies provide the rationale for antioxidant treatment of breast cancer to reprogram TAM from pro-tumorigenic M2-like TAM phenotype to a more tumoricidal M1-like phenotype. Citation Format: Brandon Griess, Kaustubh Datta, Melissa Teoh-Fitzgerald. Antioxidant therapy reprograms macrophages from protumor M2 to antitumor M1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-212. doi:10.1158/1538-7445.AM2017-LB-212